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/** \page tutorial_07b Deleting geometry elements

This small example shows how to remove faces and vertices from a mesh.

We basically use the geometry created in \ref tutorial_01.

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If we want our mesh class to be able to remove vertices, faces or edges
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we have to extend the default traits for our mesh class.
Vertices, faces and (half-)edges need the OpenMesh::Attributes::Status attribute
which is used to hold the flag "deleted" if an element is deleted.

The struct which defines the mesh traits then looks like this:

\dontinclude delete_geometry.cc
\skipline struct
\until };

After having created the geometry of the cube one can delete faces and vertices
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by simply calling delete_vertices() (delete_faces() or delete_edges() respectively).
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Note that there is actually no way to delete halfedges directly since they are automatically
affected when the parent edge is marked as deleted!

The status whether an element is marked as deleted can be requested by

\code
mesh.status(handle).deleted();  // true if element handle is marked as deleted
                                // false otherwise
\endcode

where handle is either a vertex-, edge- or face-handle.

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In this example we delete all faces except one and the corresponding vertices.
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The code looks like this

\dontinclude delete_geometry.cc
\skipline // Delete face 0
\until mesh.delete_vertex(vhandle[3], false);

Now the deleted faces and vertices are marked as "deleted" internally.
Call garbage_collection() to definitely remove them from memory.

\dontinclude delete_geometry.cc
\skipline // Delete all
\until mesh.garbage_collection();

The full source code of the example:

\include delete_geometry.cc

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**/